Lecture 17 - Endocrine System 1 Flashcards by Shazeeda Ahmad

The endocrine system primarily maintains _____________ regulation of homeostatic imbalances via hormonal controls

Long-term

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The endocrine acts with what system to coordinate and integrate the activity of body cells?

Nervous system

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The endocrine system influences metabolic activities by means of _____________ transported in the blood.

Hormones

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Responses of the endocrine system occur more slowly but tend to last longer than those of the _________________

Nervous system

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Primary endocrine glands include pituitary, parathyroid, pineal and what other two glands?

Thyroid and adrenal

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Some organs such as the ___________ and ___________ produce both hormones and exocrine products (sweat & saliva).

Pancreas and gonads

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The ______________ has both neural and endocrine functions.

Hypothalamus

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Long-distance chemical signals that travel in the blood or lymph

Hormones

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Chemicals that exert effects on the same cells that secrete them

Autocrines

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Locally acting chemicals that affect cells other than those that secrete them

Paracrines

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______________ and _____________ are local chemical messengers and will NOT be considered part of the endocrine system.

Autocrines; Paracrines

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2 main classes of hormones

Amino-acid based hormones and steroids

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___________________ are amines, thyroxine, peptides and proteins

Amino-acid based hormones

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_________________are synthesized from cholesterol. Examples include gonadal and adrenocortical hormones.

Steroids

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True or false: Hormones can alter plasma membrane permeability of membrane potential by opening or closing ion channels on target cells.

True

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True or false: Hormones stimulate synthesis of lipids or regulatory molecules on target cells.

False (proteins, not lipids)

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True or false: Hormones activate or deactivate enzyme systems on target cells

True

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True or false: Hormones induce secretory activity on target cells.

True

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True or false: Hormones stimulate meiosis on target cells.

False (mitosis, not meiosis)

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2 types of hormones

Water-soluble and lipid-soluble hormones

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Water-soluble hormones are all amino-acid based hormones except ___________________.

Thyroid hormone

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__________________ hormones cannot enter the target cells.

Water-soluble

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Instead, water-soluble hormones act on ________________, coupled by G proteins to intracellular second messengers that mediate the target cell’s response.

Plasma membrane receptors

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____________________ are steroid and thyroid hormones.

Lipid-soluble hormones

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Lipid-soluble hormones act on _____________________ that directly activate genes.

Intracellular receptors

____________________ are transported into the cell and bind to nuclear receptors.

Thyroid hormones

One of the main signaling pathways activated by water-soluble hormones/ligands is the ____________________

cAMP signaling pathway

List the steps of the cAMP signaling pathway.

1. Hormone (1st messenger) binds to receptor. 2. Receptor activates G protein. 3. G protein activates adenylyl cyclase 4. Adenylyl cyclase converts ATP to cAMP (second messenger) 5. cAMP activates protein kinases 6. Activated protein kinases can phosphorylate other proteins or trigger other cellular responses.

Once cAMP is used, it is rapidly degraded by the enzyme ___________________.

Phosphodiesterase

Intracellular enzymatic cascades (of the cAMP pathway) have a huge ______________ effect.

Amplification

___________________ mechanism is used by some amino acid-based hormones in some tissues

PIP2-Calcium signaling

PIP2-Calcium signaling involves a G protein, which activates the enzyme _______________.

Phospholipase C

Phospholipase C splits the membrane phospholipid into 2 second messengers. What are they?

DAG and IP3

___________ activates protein kinases; ____________ triggers release of calcium (Calcium alters enzymes or channels or binds to the regulatory protein calmodulin).

DAG; IP3

Steps of steroid and thyroid hormone

1. Diffuse into their target cells and bind with intracellular receptors. 2. Receptor-hormone complex enters the nucleus and binds to a specific region of DNA. 3. This prompts DNA transcription to produce mRNA. 4. The mRNA directs protein synthesis

True or false: Target cells must have the specific receptors to which the hormone binds.

True

ACTH receptors are only found on certain cells of the _____________

Adrenal cortex

___________ receptors are found on nearly all cells of the body; it is the major hormone that triggers increased metabolism.

Thyroxin

Target cell activation depends on 3 factors:

1. Blood levels of the hormone 2. Relative number of receptors on or in the target cell 3. Affinity of binding between receptor and hormone

Target cells form more receptors in response to the hormone

Up-regulation

Target cells lose receptors in response to the hormone

Down-regulation

Hormones circulate in the blood either free or bound: - ___________ and ____________ are attached to plasma proteins - All others circulate without carriers

Steroids; thyroid hormone

The concentration of a circulating hormone reflects the ______________ and speed of inactivation and removal from the body.

Rate of release

Hormones are removed from the blood by:

1. Degrading enzymes 2. Kidneys 3. Liver 4. Half-life

The time required for a hormone's blood level to decrease by half

Half-life

One hormone cannot exert its effects without another hormone being present

Permissiveness

More than one hormone produces the effects on a target cell

Synergism

What is it called when one or more hormones opposes the action of another hormone? An example of this would be ________________.

Antagonism; insulin and glucagon

Blood levels of hormones are controlled by ______________ systems, and vary only within a narrow desirable range.

Negative feedback

Hormones are synthesized and released in response to these 3 types of stimuli.

1. Humoral 2. Neural 3. Hormonal

Changing blood levels of ions and nutrients (metabolites) directly stimulate secretion of hormones.

Humoral stimuli

An example of humoral stimuli: declining blood calcium concentration stimulates the parathyroid glands to secrete PTH. PTH causes ________________ to rise and the stimulus is ________________.

Calcium concentrations; Removed

Nerve fibers stimulate hormone release

Neural stimuli

Example of neural stimuli: sympathetic nervous system fibers stimulate the adrenal medulla to secrete ______________.

Catecholamines

Hormones stimulate other endocrine organs to release their hormones

Hormonal stimuli

An example of hormonal stimuli: 1. Hypothalamic hormones stimulate the release of most anterior pituitary hormones. 2. Anterior pituitary hormones stimulate targets to secrete still more hormones. 3. Hypothalamic-pituitary-target endocrine organ ____________ feedback loop: hormones from the final target organs ______________ the release of anterior pituitary hormones.

Negative; inhibit

The ________________ modifies the stimulation of endocrine glands and their negative feedback mechanisms.

Nervous system

Example of nervous system modulation: under severe stress, the hypothalamus and the _______________ nervous system are activated. As a result, body _________________ levels rise

Sympathetic; glucose

The pituitary gland (hypophysis) has 2 major lobes

Posterior and anterior

Posterior pituitary has pituicytes (glial-like supporting cells) and nerve fibers - more for storage of neurohormones _____________ and ___________.

Oxytocin; ADH

Posterior lobe is a downgrowth of hypothalamic ________ tissue.

Neural

The posterior lobe acts as a neural connection to the ________________.

Hypothalamus

Nuclei of the _________________ synthesize neurohormones oxytocin and antidiuretic hormone (ADH), which are then transported to the _________________.

Hypothalamus; Posterior pituitary

The anterior lobe originates as an out-pocketing of the _____________.

Oral mucosa

The anterior pituitary has a hypophyseal portal system, consisting of many capillaries. It contains a large amount of capillaries because its cells are better than the posterior pituitary at responding to ____________________.

Negative feedback loop

True or false: The hypothalamus carries releasing and inhibiting hormones to the anterior pituitary to regulate hormone secretion.

True

6 hormones of the anterior pituitary

1. GH 2. TSH 3. ACTH 4. FSH 5. LH 6. PRL

All anterior pituitary hormones are what type of compound?

Protein

All anterior pituitary hormones, except _________, activate cyclic AMP second-messenger system at their targets.

TSH, ACTH, FSH, and LH are all ___________ hormones (regulate the secretory action of other endocrine glands).

Tropic

GH (Growth hormone) is produced by somatotrophs; it stimulates most cells, but targets ____________ and ____________.

Bone; skeletal muscle

GH promotes protein synthesis and encourages use of fats for fuel; most effects are mediated by ________________________.

Insulin-like growth factors (IGFS)

Low doses of GH in older age can help prevent ______________ by preventing muscle loss and osteoporosis.

Aging

GH is regulated by

Growth hormone-releasing hormone and growth hormone-inhibiting hormone (somatostatin)

GH directly stimulates liver, skeletal muscle, bone, and cartilage to produce _____________.

Insulin-like growth factors

True of false: GH directly mobilizes fats and elevates blood glucose by decreasing glucose uptake and encouraging glycogen breakdown (anti-insulin effect of GH)

True

Hypersecretion of GH results in _______________ in children and _______________ in adults.

Gigantism; Acromegaly

Hyposecretion of GH results in _______________ in children.

Pituitary dwarfism

__________________ is produced by thyrotrophs of the anterior pituitary.

TSH (Thyroid-stimulating hormone)

True or false: TSH stimulates the abnormal development and secretory activity of the thyroid.

False (normal, not abnormal)

TSH is stimulated by thyrotropin-releasing hormone (TRH). TRH is ________________ by rising blood levels of thyroid hormones that act on the pituitary and hypothalamus (negative feedback).

Inhibited

______________________ is secreted by corticotrophs of the anterior pituitary.

ACTH (Adrenocorticotropic hormone)

True or false: ACTH stimulates the adrenal cortex to release corticosteroids.

True

ACTH release is triggered by hypothalamic corticotropin-releasing hormone (CRH) in a __________________: - -> Levels peak in the morning - -> Rising levels of glucocorticoids feed back and block receptors of CRH and ACTH

Daily rhythm

Internal and external factors such as fever, hypoglycemia, and stressors can alter the release of __________________.

CRH

______________________ include FSH (follicle-stimulating hormone) and LH (luteinizing hormone).

Gonadotropins

____________________ are secreted by gonadotrophs of the anterior pituitary.

Gonadotropins

_____________ stimulates gamete (egg or sperm) production.

FSH

_____________ promotes production of gonadal hormones.

True or false: Gonadotropins (FSH and LH) are absent from the blood in prepubertal boys and girls.

True

Gonadotropin release is triggered by the gonadotropin-releasing hormone during and after ________.

Puberty

Secreted by lactotrophs of the anterior pituitary

Prolactin (PRL)

True or false: Prolactin is primarily controlled by prolactin-inhibiting hormone (dopamine).

True

Blood levels rise toward the end of pregnancy. _____________ stimulates prolactin release and promotes continued milk production.

Suckling

True or false: If suckling is not induced, PRL is not released in great quantities and the woman will stop lactating within a week. Thus suckling is essential to PRL release.

True